Astrophysics: What Hit Siberia?

Whatever it was that rocked Central
Siberia back in 1908, echoes of the explosion still reverberate in
scientific argument. Farmers 40 miles away from the center of the blast
were knocked down by the pressure wave and burned by the flash; trees
30 miles from the center were blown over. But no one is yet sure what
actually happened.

Writing in Nature, Physicist Clyde Cowan of Catholic University of
America, along with Geophysicist Chandra Atluri and Nobel Prizewinning
Chemist Willard Libby of U.C.L.A., offer the most ingenious theory so
far. After disposing...